On Resonances and Harmonics in HVDC-MMC Station Connected to AC Grid

Resonance and harmonic phenomena can occur when HVDC and Flexible Alternating Current Transmission System devices are inserted into ac grids. Frequency response analysis and electromagnetic transient (EMT) type simulations of converter stations are essential for analyzing and preventing negative effects. This paper presents two approaches for deriving the high frequency response of a converter station: using simplified analytical representation and accurate EMT-type model. Validations with control parameter impacts are presented. This paper also presents a test case, based on a recent HVdc project, where potential resonances can occur between the converter station and its ac network. It is demonstrated analytically that these resonances are mainly due to control system parameters and ac network configurations.